fs: mark the iomap argument to __block_write_begin_int const

__block_write_begin_int never modifies the passed in iomap, so mark it
const.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/buffer.c

@@ -1912,7 +1912,7 @@ EXPORT_SYMBOL(page_zero_new_buffers);
 
 static void
 iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
-		struct iomap *iomap)
+		const struct iomap *iomap)
 {
 	loff_t offset = block << inode->i_blkbits;
 
@@ -1966,7 +1966,7 @@ iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
 }
 
 int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
-		get_block_t *get_block, struct iomap *iomap)
+		get_block_t *get_block, const struct iomap *iomap)
 {
 	unsigned from = pos & (PAGE_SIZE - 1);
 	unsigned to = from + len;

fs/internal.h

@@ -48,8 +48,8 @@ static inline int emergency_thaw_bdev(struct super_block *sb)
 /*
  * buffer.c
  */
-extern int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
-		get_block_t *get_block, struct iomap *iomap);
+int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
+		get_block_t *get_block, const struct iomap *iomap);
 
 /*
  * char_dev.c